Electrodeposition of bright nickel



United States Patent 3,349,015 ELECTRODEPOSITION 0F BRIGHT NICKE Frank Passal, Detroit, Mich., assignor to M & T Chemicals Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed July 17, 1963, Ser. No. 295,818 9 Claims. (Cl. 204-49) This invention relates to electroplating nickel and more particularly to the electrodeposition of bright nickel.

Nickel electrodeposits as plated from Watts, high chloride, fluoborate, etc. type baths are not bright when plated in thickness substantially greater than those of very thin strike or flash coatings. Such deposits do not increase in luster with increasing thickness but rather decrease in brightness until dull matte deposits are obtained. To ob tain thick bright deposits from such baths, it is necessary to add certain additives, commonly of organic nature, which assist in producing highly lustrous deposits with good rate of brightening. It is a common characteristic of such so-called bright nickel plating baths that the deposits tend to increase in luster with increasing thickness. A particular advantage of these bright nickel baths is that bright deposits can be obtained on basis metals which have not been polished or which do not have a high starting luster, within reasonable specification thickness of nickel. Other concomitant advantages such as leveling or the ability of the deposits to fill in pores, scratches, or other superficial defects of the basis metal, may also be obtained.

Addition agent useful as bighteners in nickel plating baths are generally divided into two classes on the basis of their predominant function. Primary brighteners are materials used in very low or relatively low concentration, typically 0.0020.2 g./l., which by themselves may or may not produce visible brightening action. Those pri mary brighteners which may exhibit some brightening effects generally also produce deleterious side effects such as reduced cathode efficiency, poor deposit color, deposit brittleness and exfoliation, very narrow bright plate range, or failure to plate at all on the low current density areas. Secondary brighteners are materials which are ordinarily used in combination with primary brighteners but in appreciably higher concentration than that of the primary brightenerstypically 1 g./l. to 30 g./l. These materials, by themselves, may produce some brightening or grain refining effects, but the deposits are not usually mirror bright and the rate of brightening is usually inadequate.

Ideally, when primary and secondary brighteners of properly chosen and compatible nature are combined it is possible to obtain, over a wide current density range, ductile, leveled deposits which exhibit a good rate of brightening. The rate of brightening and leveling may vary in degree depending on the particular cooperating additives chosen and their actual and relative concentrations. A high degree of rate of brightening and leveling is generally desirable, particularly where maximum luster is desired with minimum nickel thicknesses. The concentrations of the secondary brighteners may usually vary within fairly wide limits. The concentrations of the primary brighteners must usually be maintained Within fairly narrow limits in order to maintain desirable properties including good ductility, adequate coverage over low current density areas, etc. Any bright nickel system which can be rendered more tolerant to fluctuations in primary brightener concentrations will have obvious advantages, particularly since the low concentration of primary brighteners and the intrinsic chemical nature of some make strict control by chemical analysis diflicult. A primary brightener which can be used over a wide range of concentration is of great value in bright nickel plating.

It is an object of this invention to provide improved nickel plate by use of a new class of superior primary 3,349,015 Patented Oct. 24, 1967 brighteners. It is a further object of this invention to provide an eflicient process for electrodepositing bright and smooth nickel deposits. Another object of this invention is to provide bath compositions for nickel plating from which bright nickel electrodeposits are obtained. Other objects of this invention may be apparent to those skilled in the art on inspection of the following description.

In accordance with certain of its aspects, the process of this invention comprises electrodepositing nickel from nickel-containing baths containing a secondary brightener; and a primary brightener having the following structure:

wherein R is a hydrocarbon radical, typically on aliphatic radical, preferably selected from the group consisting of CH -CH CH=CH, and CEC-, wherein o is the phenyl group, C H wherein x is 0 or 1, wherein A is a cyano-hydrocarbon radical, typically an omegacyano aliphatic radical, preferably having less than about 20 carbon atoms, and more preferably a cyano-hydrocarbon radical of the formula CN or (CH ),,CN wherein a is an integer from 1 to 10, and wherein B is selected from the group consisting of hydrogrogen, (CH ),,CN wherein a is an integer 1-10', and saturated or unsaturated hydrocarbon radicals having less than 6 carbon atoms.

A may be, for example, CN, or CH CN,

C H CN, -C H CN, C H CN, etc. depending upon the value of a in the range 1-10. Typically B may be methyl, ethyl, vinyl, ethynyl, n-propyl, isopropyl, allyl, 2- propyn-l-yl, propyn-2-yl, n-butyl, isobutyl, t-butyl, secbutyl, etc. The preferred compounds may be those wherein R may be CH=CH or -CEC, wherein A may be CH CN or CH CH CN; and B may be hydrogen or saturated or unsaturated hydrocarbon radicals having less than 6 carbon atoms.

Typical compounds of this class which may be effective as primary brighteners are the following:

TABLE I mo moopw The novel class of primary brighteners of this invention when used in combination with (a) suitable secondary brighteners or (b) secondary and secondary auxiliary brighteners, may give brilliant nickel deposits which have excellent ductility, good low current density coverage and luster, good rate of brightening, and good leveling characteristics. It is a particular feature of this invention that the preferred novel primary brighteners may be used over a wide range of concentration with attainment of good low current density coverage and ductility of the deposits.

Another outstanding advantage is that these novel primary brighteners can withstand long electrolysis with- 3 out build-up in the nickel plating bath of harmful decomposition products. Prior art nickel plating techniques include the use of a number of aliphatic saturated and unsaturated cyano compounds as primary brighteners;

355. The control and operating conditions, including the concentrationof the bath ingredients, pH, temperature, cathode current density, etc., of these conventional baths are generally applicable to the present invention. Pracbut they produce rapid accumulation of harmful decom- 5 tically 'all baths for electroplating bright nickel contain position products on electrolysis; they give deposits of nickel sulfate; a chloride, usually nickel chloride; a bufpoor ductility; they give inferior vlow current density fering agent, usually boric acid; and a wetting agent, e.g. coverage; they have impractically narrow usable concensodium lauryl sulfate, sodium lauryl ether sulfate, or tration limits; they create objectionable sensitivity to mosodium 7-ethyl-2-methyl-4-undecanol sulfate. Such baths mentary current interruptions, resulting in deposits in 10 include the Well-known Watts bath and the high chloride which one layer peels from another; and they have limited bath. Other baths may. contain, as the source of the nickel, compatibiliti'es with other commonly used additives. The a combination of nickel fluoboratewith nickel sulfate and compounds of this invention,cyano derivatives of aronickel chloride, or a combination of nickel fluoborate matic amides, do not have these defects and, in addition, with nickel chloride. Typical Watts-type baths and high exhibit economically low rates of consumption. chloride baths are noted in Tables II and III.

The primary brighteners of this invention may be used in concentrationsof 0.002 g./l. to 0.1 g./l., the particular TABLE H' WATTS TYPE BATES concentration chosen depending on the particular types Nickel Sulfate --g' 200 to 400 and concentration of secondary and secondary auxiliary Nickel Chloride 30 to 75 brighteners used, and also on such factors as the concen- Boric acid 30 to 50 trations of nickel sulfate, nickel chloride, and boric acid; Temperatuffi 38 to 65 operating conditions with respect to temperature and Agitationdegree of agitation; degree of luster, rate of brightening P t0 and leveling desired; and the finish of the basis metal. TABLE CHLORIDE BATHS It is preferred to use between 0.005 g./l. and 0.06 g./l.

Secondary brighteners (typically present in amount of Nl'ckel chlol'lde 150m 300 1 g/l. to 75 g./l., and preferably 1 g./l. to 20 g./l.) which NICIFCI slflfate 40 to 150 are useful in combination with the primary brighteners, Bone acld to 50 are generally aromatic sulfonates, sulfonamides or sult Telflwmture 65 fimides which may include such substituted aromatic com- 30 Agltatlonpounds as 1,3,6-naphthalene trisulfonate, sodium or po- PH fidectmmetncfl to tassium Salts of saccharill, Sodium Potassium Salts of Best plating results are usually achieved in the electroorthosulfo-benzaldehyde, benzene sulfonamide, benzene d i i process h there i used a method f monoslllfonate, For use in g Chloride yp nickel venting the thin film immediately adjacent to the cathode Plating baths, a Preferred secondary bl'ightenef y from becoming depleted in cation content. This is desira sodium or potassium salt ofsultonated dibenzothiophene bl li h d by agitation such as by i i i diOXide, P p y sulfonating p y With fuming solution pumping, moving cathode rod, etc. Sulfuric acid 01611111) for about 2 hours, isolating For the purpose of givingthose skilled in the art a betthe reaction P and neutralizing Th6 Predominant ter understanding of the invention, illustrative examples reaction product is believed to be the compound contain- 40 r i n, I each of the examples, an aqueous acidic ing three sulfonic acid p together with some mononickel-containing bath Was made up with the specified and iii-Substituted components- Th6 secondary brightene'l's components. Electrodeposition of nickel was carried out are generally Characterized y having at least 0116 sulfone by passing electric current through an electric circuit cornor sulfonic acid group attached to a nuclear carbon of a r prising a ick l anode and a sheet metal or rod cathode, homocyclic aromatic ring. both immersed in the bath. The baths were agitated, usu- Auxiliary Secondary bfightenefs Such as -P ally by a moving cathode. Bright electrodeposits were obp sulfonate, Sodium-3'chlofo'z-butene-1-5l11f0nate, tained in all the tests included herein as examples. mixed isomer of sodium-3-butene-2-hydroXy-l-S111f0nate In Example 1 through 22 inclusive, the following standand sodium-3-butene-l-hydroxy-2-sulfonate, prepared by d b th was used as base solution: reacting butadiene monoxide with sodium sulfite; or phen- G./l. yl propiolamide may be used in conjunction with the g./l. secondary brightener or brighteners. Nickel sulfate 300 Conventional baths and processes for electroplating Nickel l l i 60 bright nickel are described in Principles of Electroplating S acid 45 and Electroforming, Blum and Hogaboom, pp. 362-381, Sodlum laufyl Sulfate revised third edition, 1949, McGraw-Hill Book Co., Inc., The primarybrightener is identified from Table 1, supra. New York; and in Modern Electroplating, edited by In the following examples asd signifies amperes per A. G. Gray, The Electrochemical Society, 1953, pp. 299- square decimeter. The pH figures are electrometric values.

TABLE IV Ex. Additives Amt. CD, pH Temp. No. (g./l.)' (asd) C.)

1 Saccharin (as K salt), 4 4. O 4. O 55 Primary Brightener A 0.008 2 Saceharin (as K salt) 2 4. 0 4. 0 55 Benzene sullonamide 2 Primary Brightener A 0. 008 3 Sulfonated.dibenzothiophene dioxide 4 4.0 4.0 58' dioxide (as Na salt). Primary Brightener A 0. 020 4 Sodium-1,3,6-naphthalene tflsulfonate- 15 4.0 3.8 58 Primary Brightener A 0.016 5 Saceharin (as K salt) 4 4. 0 4. 0 55 Primary Brightener B 0. 012 6 Saceharin (as K salt)-.. 4 4. 0 4.0 55 Mixed isomer of sodium S-butene-Z- 2 hydroxy-l-sultonate and sodium 3- butene-1-hydroxy-2-sulfonate. Primary Brightener B 0. 012

TABLE IV -0outinued 1 Ex. Additives Amt. CD, pH Temp. N o. (g./l.) (asd) C.)

7 Saccharin (as K salt) 4 4. 0 3. 8 60 Phenyl propiolamide... Primary Brightener B 8 Saccharin (as K salt) Sodium-3-chloro-Z-butene-l-sulfouate. Primary Brightener C 9 Saocharin (as K salt) Phenyl propiolamide Primary Brightener 10 Saceharin (as K salt) Sodium 2-propene-1-suli'0nate Primary Brightener C 11 Sacoharin (as K salt) Mixed isomer of sodium 3-bute11ehydroxy-l-sulfonate and sodium 3- butene-1-hydroxy-2-sulfonate. Primary Brightener C 0.032 12 Saccharin (as K salt) 4 4.0 4.0 55 Primary Brightener D 0. 012 13 Sulfonated dibenzothiophene dloxide 4 4. 0 3. 5 55 dioxide (as Na salt). Primary Brightener E 0. 016 14 Sulfonated dibenzothiophene dioxide 4 4.0 3.8 58

(as Na salt). Primary Brightener F 0.016 15 Sulfonated dibenzothiophene dioxide 4 4.0 3. 5 55 (as Na Salt). Phenyl propiolamide 0. 16 Primary Bn'ghtener F 0.008 16 Sulfonated dibenzothiophene dloxide 4 3. 5 3.5 55

(as Na salt). Primary Brightener G 0.040 17 Saceharin (as K salt) 4 4 0 4. 0 55 Mixed isomer of sodium 3-butene-2- 2 hydroxy1-sulfonate and sodium 3 butene-l-hydroxy-Z-sulfonate. Primary Brightener H 0.050 18 Sulfonated dibenzothiophene dioxide 4 4. 0 4. 0 55 (as Na salt). Primary Brightener I 0.010 19 Sulfonated dibenzothiophene dioxide 4 4.0 4.0 55

(as Na salt). 7 Phenyl propiolamide 0.16 Primary Brightener I 0.010 20 Saccharin (as K salt) 4 4.0 4. 0 55 S0dium-3-chloro-2-butene-1-su1fonate 4 Primary Brightener .T 0. 015 21 Saccharin (as K salt) r 4 4. O 3. 5 55 Mixed isomer of sodium 3-butene-2- 2 hydroxy-l-sulfonate and sodium 3- butene-l-hydroxy-2-sulfonate. Primary Brightener K O. 060 22 Saceharin (as K salt)". 4 Phenyl propiolamide 0. 16 Primary Brightener K 0.040

The compounds designated L, M, and N supra, were The foregoing examples illustrate speclfic baths and also used in similar baths and similar bright electrodeprocesses. It is understood that the compositions and conposits were obtained. d1t1ons may be varled. Although the potassium and sodium In Example 23 to 26 inclusive, the followlng standard salts were most often used and are preferred, they may be bath was used as a base solution: partially or completely replaced by such other salts as G./l. nickel, magnesium, etc. salts. Nickel chloride 250 The nickel electrodeposits obtained from baths utrhz- Nickel sulfate 45 mg the novel brlghtener combmatlon are advantageous Boric acid 45 m that mirror-bright lustrous electrodeposits havmg a Sodium lauryl sulfate 0. 5 hlgh degree of ductility are obtamed over a wide range TABLE V Ex. Additives Amt. CD, pH Temp. No. (g./l.) (asd) C.)

23 Saccharin (as K salt) 2 4.0 4. 5 55 Sodium 3-chlor0-2butene-1sulfonate Primary Brightener C 24 Saccharin (as K salt) Sochum-3-chloro-Z-butene-l-sulfonate- Primary Brightener J 25- Sulfonated dibenzothiophene dioxide (as Na salt). Primary Bn'ghtener C 26. Sulfonated dib enzothiophene dioxide (as Na salt). Primary Brightener J of cathode current densities. The bright nickel electrodeposits are preferably plated on a copper or copper al. loy basis metal. However, they may be electrodeposited directly on such metals as iron, steel, etc.

The novel primary brighteners of this invention may advantageously be prepared by the following reaction:

wherein Y may be selected from the group consisting of chloride and bromide and at, R, A, B and x are as defined supra. Thus, for example, when B is hydrogen the product may be a .monocyano. substituted compound; when B is cy-ano-substituted group, the product may be a dicyano substituted product.

Typical (R) CO--Y reactants which may be employed in the novel preparative process of this invention may include phenylpropioloyl chloride CEC-COC1 phenyl cinnamoyl bromide CH=CHCOB11; 3-phenylpropanoyl bromide CH CH COBr; benzoyl chloride; benzoyl bromide; etc.

Typical reactants which may find use in the process of this invention may include fl-cyanoethyl amine; N,N-di-B-cyanoethyl amine; N-allyl-N-fi-cyanoethylamine; cyanomethylamine; N-ethyl-N-cyanomethylamine; N,N-dicyanomethylamine; N-N-butyl-N ,B cyanoethylamine; hydrogen cyanamide; w-cyanopentamethyleneamine; etc. It will be apparent to one skilled in the art that reactive derivatives of the noted amines, e.g., the amine sulfates, may be substituted for the amine in this preparation.

The reaction of the acid chloride or bromide reactant With the amine reactant may typically be effected under mild conditions, preferably in the presence of a solvent or solvents. The reaction may occur readily and in high yield, typically at temperatures as low as C. or lower. The by-product HY may be removed from the reaction system by reaction with a suitable base, such as sodium hydroxide, sodium carbonate, ammonia, etc. If desired, the use of an additional base may be avoided by employing an excess of the amine reactant which may react with HY to form, e.g., the amine hydrochloride, amine hydrobromide, etc.

A typical preparation may be as follows. The amine reactant in 100% excess may be dissolved in water and the resulting solution may be added to an inert hydrocarbon solvent, say benzene. This mixture may be cooled to a low temperature, say 0 C. The acid chloride or bromide reactant may bedissolved in an inert hydrocarbon solvent, say benzene, preferably a hydrocarbon solvent whichhas previously been dried. The acid chloride solution may then be added dropwise to the amine solution with moderate stirring, and the reaction mixture may be maintained at a low temperature, say 0 0, throughout the addition. When the addition is complete, the mixture may be allowed to reach room temperature, say 2030 C., and may be stirred at this temperature for a short period of time, typically about one hour. The two layers may be physically separated and the product may be isolated from the benzenelayer by evaporation or distillation after all the residual amine or. amine hydrochloride or hydrobromide has been removed, typically by washing with water, and drying. If desired, the product may be further purified by recrystallization or distillation.

Certain of the products of this invention may also be prepared by the reaction:

wherein (p, R, B and x are as defined supra. It will be understood that when B is hydrogen, a second equivalent of acrylonitrile may be reacted to form the corresponding N,N-dicyanoethyl product.

This reaction may typically be carried out with or without the use of a suitable insert solvent, typically water. Moderate temperatures, typically 30l00 C. may be employed. Basic catalysts such as sodium hydroxide, triethylamine, etc., may be used in small amounts to accelerate the reaction. Excess acrylonitrile may be stripped off afterthe reaction is complete.

Preparation of the novel compounds of this invention may be further. illustrated by the following specific examples.

CHzCEgNC Example 27 .--N-cyan0ethylphenylpropiolamide Thirty grams of S-aminopropionitrile (B-cyanoethylamine) was dissolved in cc. ofwater and chilled in.

Example 28.-N,Nbis-/3"-cyan0,ethylphenylpropiolamide Five grams of phenylpropiolamide was mixed with 25 grams of acrylonitrile and 2 drops of a 40% by weight solution of sodium hydroxide in water. The mixture was warmed for several minutes, after which the excess acrylonitrile was stripped off. The remaining brown gum was leached out with 200 cc. of ethanol, and the resulting solution was then carbon-treated, filtered and cooled.

The oil which separated on chilling was separated and treated with petroleum ether to give 2.7 grams of soft solid. After recrystallization the product had a melting point of 97-98 C.

Analysis.--The0ry: C, 71.7%; H, 5.2%; N, 16.7%. Found: C, 71.9%; H, 5.2%; N, 16.3%.

Although this invention has been illustrated by reference to certain specific embodiments, modifications thereof which are clearly Within the scope of the invention will be apparent to those skilled in the art.

I claim:

1. A process for electrodepositing nickel which comprises electrodepositing nickel from a Watts type electroplating bath containing a secondary brightener and, as a primary brightener, an etfective amount of a compound having the structure mary brightener is present in amount of 0.002 g./l. to 0.100 g./l.

3. An aqueous acid electrolytic bath containing soluble nickel salts for the electrodeposition of nickel and containing as a primary brightener an elfective amount of a compound having the structure B wherein R is selected from the group consisting of H=CH, and C C; x is 0 or 1; A is selected from the group consisting of --CN and -CH ),,CN wherein a is an integer 1-10; and B is selected from the group consisting of hydrogen, -(CH -CN wherein a is an integer 1-10, and hydrocarbon radicals having less than 6 carbon atoms.

4. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is present in amount of 0.002 g./l. to 0.100 g./l.

5. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is N,N-bis [icyanoethyl phenylpropiolamide.

6. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is N,N-bis 25 cyanomethyl phenylpropiolamide.

7. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is N-B-cyanoethyl phenylpropiolamide.

8. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is N-methyl-N- ,B-cyanoethyl phenylpropiolamide.

9. An aqueous acid electrolytic bath as claimed in claim 3 wherein said primary brightener is N,N-bis fi-cyanoethyl cinnamide.

References lCited UNITED STATES PATENTS 2,461,842 8/1949 Olin 260465 2,781,305 2/1957 Brown 204- 49 2,781,306 2/1957 Brown 20449 2,876,177 3/ 1959 Gundel et a1. 204-49 2,881,120 4/1959 Towle et al. 204-49 2,927,126 1/1960 Pursglove 260465 3,036,112 5/1962 Lynn 260-465 3,116,316 12/1963 Rauhut 260-465 3,139,393 6/1964 Hartman et a1. 204-49 3,172,869 3/1965 Saxon 260-465 JOHN H. MACK, Primary Examiner. G. KAPLAN, Assistant Examiner. 

3. AN AQUEOUS ACID ELECTROLYTIC BATH CONTAINING SOLUBLE NICKEL SALTS FOR THE ELECTRODEPOSITION OF NICKEL AND CONTAINING AS A PRIMARY BRIGHTENER AN EFFECTIVE AMOUNT OF A COMPOUND HAVING THE STRUCTRE PHENYL-(R)X-CO-N(-A)-B WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF 